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What software do I need to run a CNC mill?
Creating a part on a CNC mill is a three phase process. The part is drawn in a
CAD (Computer Aided Design) drawing program such as AutoCAD. Then a CAM
(Computer Aided Manufacturing) program is used to convert the CAD drawing to
G-Code. Finally, the G-code controls the CNC mill as it makes the part.
We will take a look at what is involved in using these three kinds of software by
sketching out the creation of a very simple part.
Creating a CAD Drawing
There are dozens of CAD programs with which you can create a drawing. Costs
vary from free to many thousands of dollars. We are not going to get into
reviews or recommendations here, but simply describe the CAD program that
we know the best; TurboCAD. Let’s take a look at the steps required to create
a drawing.
A new drawing in TurboCAD is based on a template. In this case the template
defines an A-size (8.5 x 11”) sheet using inches for dimensions and including
the title block.
This view is the Paper view. This is the page that prints. To work on the
drawing we switch to Model view. The title block is gone and a grid appears.
This is where we create our drawing.
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To start the drawing of our sample part, use the Rectangle tool on the left side
of the drawing area to create a rectangle that is 2.5” tall and 1.5” wide. You
can use your mouse to define the corners of the rectangle, but you will quickly
find that you need to use the parameter block at the bottom of the screen to
enter the values you want if you want your drawing to be accurate. Your
finished part will not be any more accurate than your drawing.
Create a double line ¾” long and ¼” wide. Center it ½” above the bottom of
the part.
Use the Arc tool to add semi-circles to the ends of the double line. This
completes the slot.
2
Add a 1” square centered ¾” below the top of the part. Use the Fillet tool to
round the corners to 1/8” radius.
This completes the top view of the part. We need to add this view to a
separate layer so that the CAD program can differentiate this view from the
other information in this drawing. We create a layer named Top View and
assign all the elements of this view to that layer.
3
Now add the right view of the part.
Here’s what the Paper view looks like.
4
To move this file to PartMaster CAM, we save it as a DXF (Drawing eXchange
File).
The CAM Process
CAM (Computer Aided Manufacturing) software takes the CAD drawing you
created and translates it into G-code. It is an interactive process, because you
must tell the software what tools you will use, plus information such as spindle
speed, cutting depth and cutting speed.
The CAM program we are using is Dolphin PartMaster CAM. Open PartMaster
CAM and select Create a new job from a DXF file. Load the Example 1.DXF file
we created with TurboCAD.
In the DXF Import Options dialog choose Import only geometery on layer, and
enter Top View.
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The top view of the part appears in PartMaster CAM. Here we have used View >
Options to show Geometry Names.
6
In the bar on the right of the screen, click Area Clearance and Pockets. Then
click User Defined. The Pocket: Custom Shape dialog appears.
Here we tell the CAD program how to clear the square at the top of the part.
We have defined an end mill that is ¼” in diameter and set the spindle speed
to 1000 RPM. We will cut to a depth of 0.26” so we go completely through the
part in three passes.
Use Execute > Run Program to see how the program will run.
Now click the Command tab on the right side of the window and make the
settings for the slot at the bottom of the part.
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Now the machining parameters for both areas are set. Use Execute > Post
Process to create the G-code.
The program trundles for a few seconds, then produces the G-code necessary
to run this part.
( Produced
:- 19:45:18 Friday, October 23, 2009 )
( CNC File
:- Example 1 )
( Post Processor :- M_MACH3 )
( Part Number ID :- )
N5G00G20G17G90G40G49G80
N6G00G28Z0.0
N7G49
N8T1M06 ( End mill )
N9G43Z1.9685H1
N10S1000M03
N11G94
8
N12M08
N13X0.375Y2.125
N14Z0.125
N15G01Z-0.0867F1.25
N16X1.125Y2.125F5.0
N17X1.125Y1.375
N18X0.375Y1.375
N19X0.375Y2.125
N20X0.5625Y1.9375
N21X0.9375Y1.9375
N22X0.9375Y1.5625
N23X0.5625Y1.5625
N24X0.5625Y1.9375
N25X0.6563Y1.8438
N26X0.8438Y1.8438
N27X0.8438Y1.6563
N28X0.6563Y1.6563
N29X0.6563Y1.8438
N30G00Z1.9685
N31X0.375Y2.125
N32Z0.0383
N33G01Z-0.1733F1.25
N34X1.125Y2.125F5.0
N35X1.125Y1.375
N36X0.375Y1.375
N37X0.375Y2.125
N38X0.5625Y1.9375
N39X0.9375Y1.9375
N40X0.9375Y1.5625
N41X0.5625Y1.5625
N42X0.5625Y1.9375
N43X0.6563Y1.8438
N44X0.8438Y1.8438
N45X0.8438Y1.6563
N46X0.6563Y1.6563
N47X0.6563Y1.8438
N48G00Z1.9685
N49X0.375Y2.125
N50Z-0.0483
N51G01Z-0.26F1.25
N52X1.125Y2.125F5.0
N53X1.125Y1.375
N54X0.375Y1.375
N55X0.375Y2.125
N56X0.5625Y1.9375
N57X0.9375Y1.9375
9
N58X0.9375Y1.5625
N59X0.5625Y1.5625
N60X0.5625Y1.9375
N61X0.6563Y1.8438
N62X0.8438Y1.8438
N63X0.8438Y1.6563
N64X0.6563Y1.6563
N65X0.6563Y1.8438
N66G00Z1.9685
N67M09
N68G00G28Z0.0
N69G49
N70T2M06 ( End mill )
N71G43Z1.9685H2
N72S1500M03
N73G94
N74M08
N75X0.375Y0.5313
N76Z0.125
N77G01Z-0.0867F1.25
N78G03X0.4063Y0.5I0.375J0.5F5.0
N79X0.375Y0.4688I0.375J0.5
N80G01X1.125Y0.4688
N81G03X1.0938Y0.5I1.125J0.5
N82X1.125Y0.5313I1.125J0.5
N83G01X0.375Y0.5313
N84Z-0.1733F1.25
N85G03X0.4063Y0.5I0.375J0.5F5.0
N86X0.375Y0.4688I0.375J0.5
N87G01X1.125Y0.4688
N88G03X1.0938Y0.5I1.125J0.5
N89X1.125Y0.5313I1.125J0.5
N90G01X0.375Y0.5313
N91Z-0.26F1.25
N92G03X0.4063Y0.5I0.375J0.5F5.0
N93X0.375Y0.4688I0.375J0.5
N94G01X1.125Y0.4688
N95G03X1.0938Y0.5I1.125J0.5
N96X1.125Y0.5313I1.125J0.5
N97G01X0.375Y0.5313
N98G00Z1.9685
N99M09
N100M30
%
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We’re not going to teach you G-code here, but we will let you know what sort
of thing you are looking at by explaining a few of the lines in that G-code.
( Produced
:- 19:45:18 Friday,
October 23, 2009 )
( CNC File
:- Example 1 )
( Post Processor :- M_MACH3 )
( Part Number ID :- )
This is information for you, not the
CNC Milling machine. Notice that you
can read and understand it.
N5G00G20G17G90G40G49G80
N6G00G28Z0.0
N7G49
N8T1M06 ( End mill )
N9G43Z1.9685H1
N10S1000M03
N11G94
N12M08
These are all “getting started” codes.
Notice that all the lines start with N
followed by a number. This is simply
the line number and is more for you
than for the CNC machine. The CNC
machine simply executes code in the
order in which it is received.
Look at line N5. In that line things are
being set up. For example, G20 says to
use inch units, while G90 says to use
absolute distances.
Line N8 stops the CNC machine so you
can change the tool. It’s stopping for a
tool change (M06) and asking for tool
number 1 (T1). You click Start Cycle to
resume the program once you have
changed the tool.
N15G01Z-0.0867F1.25
N16X1.125Y2.125F5.0
N17X1.125Y1.375
N18X0.375Y1.375
N19X0.375Y2.125
N20X0.5625Y1.9375
N21X0.9375Y1.9375
Now we start making chips. In line
N15, G01 starts linear interpolation.
The Z axis goes to -1.086 at a 1.25
feed rate (F1.25).
The rest of the lines have X and Y
coordinates. These are the end point
for the cut for this line of code. As you
can see, lines something like these
make up most of the rest of the
program.
This is clearly not an exhaustive discussion of G-code. If you want the nittygritty, see Using Mach3Milll on http://www.machsupport.com.
PartMaster CAM saved the G-code in a file with a PUN extension. It’s in the
folder in which you saved your drawing.
Creating the Part
You now have the definition of the part in a language that the CNC milling
machine can understand; G-code. If you were using a commercial CNC machine
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such as a HAAS Vertical Machining Center , the controller would be built into
the machine and you would transfer the G-code directly to the machine. Most
hobby CNC machines have an external controller; a personal computer that is
cabled to the CNC machine. A large percentage of these personal computers
are running the Mach 3 machine control program.
Let’s briefly see how Mach 3 works. Use a USB Flash Drive to move the G-code
file to the computer connected to the CNC milling machine. You probably want
to put it in C:\Mach3\GCode.
Start Mach 3 using the profile that is appropriate to your CNC machine. In our
case, we will use the KX3 profile, appropriate for the LittleMachineShop.com
model 3503 CNC Milling Machine.
This screen is the Mach 3 machine controller. You can confirm the profile in the
lower right corner. Let’s load the G-code, and then look at this screen. Click
Load G-Code and select the Example 1.pun G-code file.
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Now we can see what those empty rectangles are for on the screen. In the
upper-left corner is the G-code file we are working with. In the upper-center is
the DRO; the digital read out. This shows the current position of the four axes.
In the upper-right corner is the tool path. This window shows the projected
path of the tool and shows its current position as it progresses through the
program.
The lower-left panel incorporates most of the controls you need to load and
execute a G-code program. The Reset button is the on-screen E-Stop, or
Emergency Stop button. This button (and the hardware E-Stop button on the
machine) will stop the machine immediately. You will use these buttons a lot
as you learn CNC programming.
Cycle Start does what you expect; it starts executing the program. It also restarts execution from the current position after a tool change, Stop or Pause.
Feed Hold pauses execution, while Stop stops it. Cycle Start resumes after
either one. Be careful when resuming any programs, because changes you have
made manually (such as stopping the spindle) are not reversed. The program is
simply executed from the current line.
The Tool Information provides just the information you would expect; which
tool you are using (or which tool is requested if the Change Tool bar is lit), and
information about that tool.
The Feed Rate block shows the current feed rate and allows you to override the
program settings. Like wise, the Spindle Speed block shows the current spindle
speed settings and allows you to control the spindle speed.
If you press the Tab key, the MPG “Pendant” appears. This is an on-screen
representation of an MPG (Manual Pulse Generator) pendant, a hand-held
control on some CNC machines. This screen allows you to manually control the
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four axes and the spindle. For example, to move the Z-axis up, hold the Z+
button down with your mouse.
We’ve skipped lots of steps to get to this point. For example, we have said
nothing about the physical aspects of mounting your work piece and cutting
tools in the CNC milling machine. And we haven’t addressed how to tell the
CNC machine where your part blank and the cutting tool are located (hint, see
the Offsets screen in Mach 3). But we did take a look at what the three major
pieces of software are that are required to make a part on a CNC machine.
Do you really need all this software?
In a word, no. There are a couple ways around using all these software
programs. You can simply write the G-code by hand. And many machine
controllers have a “conversational mode” that helps you write the G-code for
standard operations such as cutting a slot.
Hand Coding
There are, of course, other ways to do this. One can create G-code “by hand”,
by simply typing the G-code commands into a text editor such as Notepad. For
very simple projects, this may be the quickest way to make your part.
Here is the G-code to create a simple slot:
G00 X0.1375 Y0.1375
G01 Z-0.068 F30
X1.3625 F400
X1.275 Y0.05
Y0.225
14
X0.225
Y0.05
X1.275
G00 Z1
G00 X0.1375 Y0.1375
G01 Z-0.125 F30
X1.3625 F400
X1.275 Y0.05
Y0.225
X0.225
Y0.05
X1.275
G00 Z1
X0.75 Y-0.05
G01 Z-0.125 F30
Y0.15 F400
X0.125
Y0.125
X1.375
Y0.15
X0.75
Y0.05
G00 Z1
M5 M9
M30
We won’t go into what all those codes mean because a) there are quite a few
of them, and b) they mean (somewhat) different things to different CNC
machines. If you want to hand code G-code, find the G-code reference for your
machine.
Conversational Programming
Most CNC Control programs, including Mach3, have the ability to “program
themselves” using dialog boxes or wizards. This is known in the trade a
Conversational Programming. You can do things like creating bolt circles,
engraving, and other relatively standard operations.
You run a wizard or fill out a dialog box or two and the controller creates the
G-code it needs to execute the operation. This process is good for one-off
projects, but combining the output of several canned cycles into a more
complex process can be problematic.
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CAD and CAM Programs
Here are short and very incomplete lists of CAD and CAM programs. Prices
range from free (A9CAD) to several thousands of dollars. Don’t take these lists
as recommendations. These are just the programs we found in a short session
with Google and Bing.
CAD Programs
A9CAD
www.a9tech.com
Alibre
www.alibre.com
AutoCad
usa.autodesk.com
BobCAD-CAM
www.bobcad.com
DeltaCad
www.deltacad.com
Dolphin Partmaster
www.dolphincadcamusa.com
Mastercam
www.mastercam.com
SketchUp Pro
sketchup.google.com
SolidWorks'
www.solidworks.com
TurboCad
www.turbocad.com
VCarve Pro
www.vectric.com
CAM Programs
ArtCAM Insignia
www.delcam.com
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BobCAD-CAM
www.bobcad.com
Cut2D
www.vectric.com
D2nc
www.d2nc.com
Dolphin Partmaster
www.dolphincadcamusa.com
Edgecam
www.edgecam.com
FeatureCAM
www.featurecam.com
GibbsCAM
www.gibbscam.com
Mastercam
www.mastercam.com
VCarve Pro
www.vectric.com
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